Contribution to development of aerosol therapy through investigation of factors and means of control of medical aerosol growth in respiratory system. Study is to involve (a) experimental measurement of growth rate of existing medical aerosols for various particle sizes at humidities representative of those in respiratory system, (b) development of numerical models permitting prediction of particle size of medical aerosols as a function of residence time in respiratory system, and (c) experimental investigation of means of control of growth rates of medical aerosols through use of agents affecting rates of mass transfer to aerosol particles.